1. Field of the Invention
The present invention relates to a radiation image capturing system.
2. Description of the Related Art
In recent years, FPDs (flat panel detectors) have been realized in which a radiation-sensitive layer is disposed on a TFT (thin film transistor) active matrix substrate and radiation can be directly converted to digital data. Using these FPDs and the like, portable radiation image capturing devices (below referred to as electronic cassettes) have been realized that generate image information, which represents a radiation image capturing image manifested by irradiated radiation, and store the generated image information.
Because such an electronic cassette is portable, it may photograph a patient rested on a stretcher, a bed or the like, and a location of photographing may be adjusted by altering a position of the electronic cassette. Therefore, a patient who cannot be moved may be flexibly dealt with.
However, at an FPD, charges arise even in states in which X-rays are not irradiated, because of dark current and the like, and the charges are accumulated in the pixels. Therefore, a reset operation, which reads out and erases charges that have accumulated in the pixels of an FPD during waiting, is repeatedly carried out. When instruction information requesting image capturing of a radiation image is received from a control apparatus for controlling (known as a console), the reset operation corresponding to a full frame is completed before an instruction operation instructing the start of image capturing is sent to the console. When the console receives this instruction information, the console causes X-rays to be irradiated from a radiation producing device to the electronic cassette. After a predetermined duration from the sending of the instruction information, the electronic cassette performs a read-out of charges that have accumulated in the pixels of the FPD.
However, if communications between the electronic cassette and the console are wireless communications, communication conditions may become unstable and instruction information may be delayed before being received by the console. If, for example, instruction information instructing the start of image capturing is delayed, a timing at which X-rays are irradiated from the radiation producing device to the electronic cassette is delayed, and synchronization in the timing of image capturing cannot be attained.
Accordingly, Japanese Patent Application Laid-Open (JP-A) No. 2008-132216 has disclosed a technology of, at an X-ray image capturing device (an electronic cassette), performing idling driving which repeats refreshing and blank-reading of charges of an FPD at predetermined intervals, and at an X-ray control device (a console), keeping an X-ray image capturing-possible period synchronized with an optoelectronic conversion mode period of the idling driving of the image capturing device, with a timer.
However, in the technology of JP-A No. 2008-132216, the electronic cassette simply repeats the same idling driving, and cannot deal with different image capturing modes in which the X-ray image capturing-possible period is altered. Moreover, in the technology of JP-A No. 2008-132216, if synchronization of the X-ray image capturing-possible period of the console with the electronic cassette is lost due to a single occurrence of image capturing in a different image capturing mode or a malfunction or the like, it becomes impossible to synchronize the image capturing timings. Further yet, in the technology of JP-A No. 2008-132216, if there are plural electronic cassettes, it is necessary to keep X-ray image capturing-possible periods for the plural electronic cassettes synchronized at the console.